Heck even trees and plants get it. (I have learned that tumours are not necessarily cancer.)**Here's a thought - what is the difference between a replicating single-celled organism and a single celled organism with cancer?

Quizatzhaderac wrote:What organism most distantly related to human is capable of getting cancer? Or conversely, what is the creature that is most closely related to humans that can't get cancer?

Is this what you meant?

There's specifically a myth that sharks don't get cancer, and a such someone has bothered to document sharks with cancer.So let's assume vertebrates generally are susceptible.

What about [other opisthokonts]?

You didn't ask about plants, so you seem to realize they can't get cancer (essentially because their cells aren't mobile), but they do get tumors. Fungi also can't get cancer, but for a different reason. Fungi have a single-cell stage during which cancer isn't even a coherent idea, and a multi-cell stage during most of which time cells don't even divide. If cells don't stop dividing, you don't get cancer exactly, you just fail to get a fruit.

I don't think cancer is possible in any other kingdoms. Among animals though, it should be essentially universal. It has been documented in vertebrates, crustaceans, insects, mollusks, and roundworms at least, but probably in loads of other animals, I just didn't do much research. Small animals and short-lived animals are extremely unlikely to get cancer for obvious reasons, but because they are so studied and reproduce so quickly, it has still been observed on rare occasions in some model animals like D. melanogaster and C. elegans.

It gets murkier for very simple organisms. I can't find evidence of actual malignant tumors in ctenophores or cnidarians, but I don't see why they would be evolutionarily impossible. There is at least one whimsical paper suggesting genes in ctenophores homologous with oncogenes in Homo. Some of these animals are biologically immortal though, so maybe they do have some perfect cancer immunity.

I don't know about sponges though, because I just generally don't know anything about sponges.

Eebster the Great wrote:There is at least one whimsical paper suggesting genes in ctenophores homologous with oncogenes in Homo. Some of these animals are biologically immortal though, so maybe they do have some perfect cancer immunity.

Alternately, it's "perfect cancer" that provides proper death immunity, what we¹ get is the potential for immortality (one way or another) but never in a 'good' way.

(The other kingdoms' different approaches to cells and cell division/tasking go hand in hand with how they inhabit their niche. Reproduction by cladaptosis, rhizomic fragmentation and the like is a very good plant strategy that would be ill-fitted to animals of any complexity, and nightmare fuel in many situations. And I'm sure if the users of this forum were somehow of the plant clade, or other alternative, they'd be wondering about a different health issue and talking about how animals have this different setup that made them not susceptible. )

¹ The rest of the animal kingdom, that is. There's nothing special about humans other than perhaps the post-reproduction longevity that doesn't really enable natural selection against any post-prime and gerontic disease incidence. Those which don't normally apply to creatures only because they tend to be killed or die from other macro threats before their own cells go so noticeably rogue. Tasmanian Devils being a noted exception, but mostly for being such a rare exception, and in a transmissable manner too. Pets and other animals under our care are similarly coddled beyond a 'natural lifespan in the wild' so are subject to similar issues.

Post-menopausal grandmotherin in humans/orca/etc (or the perhaps the potential loss of it) will give microbenefits to the continued development of healthy superannuation, so may have promoted gene-variations that suppresses the more suicidal packages of genes just a little bit, though medical developments and more generalised societal welfare mitigate the immediate selection pressures so perhaps we're still only as susceptible as if we just hadn't died of environmental factors. Perhaps once we can reliably get in there and use our knowledge to manipulate our genomes sufficiently well to act upon the causal elements (rather than merely patch up problems that arise and are discovered in time) then perhaps our artificial selection will make it a fait accompli. Apart from every other threat to our immortality.

LaserGuy wrote:According to this report, tumors or tumor-like diseases have been found in such species as coral, roundworms, mollusks, insects, etc. So... it looks like basically everything.

That's a good article, and one of the main things is it acknowledges can/can't get cancer isn't a strict binary. Multiple cases with invertebrates were listed where malignant and metastasized cancers hadn't been observed. Also of note was that the deliberate human induction of tumors in nematodes was discussed, but not the natural occurrence. Of particular note is the statement "With the possible exception of bivalves and drosophila, evidence of metastasis is absent in invertebrates,"

Eebster the Great wrote:You didn't ask about plants..

I didn't ask about plants because they evolved multi-celluarity separately from animals.

For my purposes, I would then presume anything in plants that looks like cancer is merely analogous to cancer, rather than "true" cancer. But that facts of cell immobility and the mechanical and structural flexibility and durability of plants makes analogues less likely.

Sponges and fungi have a lot of a plants flexibility (they aren't going to die from an obstructed coronary artery, because no such small structure exists that is needed to live).

The thing about recursion problems is that they tend to contain other recursion problems.

Fine, but evidence of cancer in mollusks is not controversial to my knowledge. Here's another study of cancer in claims. It may be due to an environmental contaminant of human origin, but if a chemical pollutant can induce cancer in clams, it can probably happen naturally. Mussels are apparently used as bioindicators for carcinogens. It's hard to imagine why they wouldn't get cancer.

Just to be clear, I acknowledge mollusks and nematodes get neoplasms; I'm just drawing a bunch of lines between "gets cancer at all" and "gets cancer, just like humans". Some of the hallmarks of the human experience of cancer are the natural potential for malignancy, metastasis, and mortality.

I'm also not saying "if we haven' t seen it, it doesn't happen". In a lot of these cases the kind of studies I'd be interested in simply haven't been done. I'm merely skeptical about making huge categorical inferences.

The thing about recursion problems is that they tend to contain other recursion problems.

It describes it as "gonadal cancer" and points out that they can transform other cells into cancer in mice. I am sure they don't get cancer "just like humans," but they do get malignant neoplasms. I'm not fully understanding the distinction you're trying to draw.

Some organisms very rarely get cancer, like lobsters. Some, like C. elegans, can only get gonadal cancer because there are no somatic stem cells in adults. Others, like D. melanogaster, can get it frequently under the right conditions. But as far as I know, there is no evidence there are any animals that cannot get cancer under any conditions whatsoever. Perhaps there are some (sponges, T. adhaerans, who knows?), but they are probably very simple.

Eebster the Great wrote: I'm not fully understanding the distinction you're trying to draw.

Since this isn't a practical question, I'm trying to draw as many distinctions as I can. For the sake of conversation, the following distinctions seem important to me now:

Can the organism develop neoplasms? Yes for Bileteria, maybe for sponges and fungi.

Can the mass effect of a begin tumor critical endanger the organism? Yes, for anything with a brain, probably much less likely with simpler organisms.

Can these tumors metastasize?

Can these tumors be malignant other ways? (for example LaserGuy's link indicated an analogue to leukemia in mollusks).

Do other organisms have tumor defense mechanisms we don't? Yes, naked mole rats have a cellular "anti-crowding" mechanism. Arthropods melanize tumors, for some reason. Probably others.

For organisms the grow rapidly over there whole lives, are the "uncontrolled" cells actually able to outpace normal growth dramatically/dangerously?

Regarding the quality of evidence:

Has this happened been observed without intentional inducement? (I'm counting pollution as unintentional).

Has the organism been studied enough that we would actually be able to have found natural malignancies.

Where induction has happened, how was it done, and what does that tell us about tumor formation? From what I've seen, a lot of these invertebrates studies are interested in how tumors develop, not if/ how often.

The thing about recursion problems is that they tend to contain other recursion problems.